Why is this bolt here?

[Shabah210]

Working on my 72 cb750. I purchased the bike after 10 years of little use. I found that it had really bad front brake drag. I eliminated the master cylinder suspects and disassembled the wheel cylinder. The piston was really hard to move and there was buildup around the inside of bore. I cleaned those things up and then started looking more carefully at the brake housing. There is a bolt threaded into the end of the housing and protruding slightly into the bore. I appears to be keeping the piston from seating fully down in bore. I assumed that this was a model specific but can't find any picture the shows this bolt on any other bike.
Can anyone explain?

 

[Loose Chain]

Maybe someone drilled and tapped that hole so they could put a long bolt in there to push a stuck piston out of the bore. They then put a short bolt in to plug the hole after. Have you had the bolt out? There must be something sealing it to keep it from leaking.

 

[Shabah210]

I never thought of that. Not the best solution. I found another housing. Good Thinking.

 

[Loose Chain]

I never thought of that. Not the best solution. I found another housing. Good Thinking.

Ya there is lots of those housings around.

 

[pickleknuckles]

My K4 750 had one in its original caliper too. I assume it was done to push the piston out at some point.